For toxicological and odorous reasons, crosslinked and non-crosslinked vinylpyrrolidone polymers should be as free as possible of unreacted monomer. The absence of vinylpyrrolidone residual monomer is particularly significant for cosmetic and pharmaceutical applications; however, conventional methods for minimizing residual monomer content in vinylpyrrolidone polymers are only successful in obtaining a reduction to 100-1,000 ppm and are directed to the separate addition of initiator and/or temperature increase toward the end of the polymerization cycle as described in U.S. Pat. No. 2,665,271 and 4,182,851. Since, these methods have not been able to reduce the residual monomer in the particulate polymeric product to a level of a few parts per million, the use of such polymers has been somewhat limited
Accordingly it is an object of this invention to provide a process for the reducing residual monomer content of a vinylpyrrolidone or vinylcaprolactam polymeric product to a level of not more than 5 parts per million (ppm) and in some cases to less than 1 ppm.
Another object of this invention is to provide an economical and commercially feasible process for producing a substantially pure vinylpyrrolidone or vinylcaprolactam polymeric product in a free-flowing particulate state.
Another object of this invention is to produce substantially pure vinylpyrrolidone polymer suitable for use in pharmaceutical and cosmetic applications
These and other objects of the invention will become apparent from the following description and disclosure.